The Arch of Galerius and the Rotunda are neighbouring early 4th-century AD monuments in Thessaloniki.
The 4th-century Roman emperor Galerius commissioned these two structures as elements of an imperial precinct linked to his Thessaloniki palace. Archeologists have found substantial remains of the palace to the southwest. These three monumental structures were connected by a road that ran through the arch, which rose above the major east–west road of the city.
The Arch of Galerius was built in 298 to 299 AD and dedicated in 303 AD to celebrate the victory of the tetrarch Galerius over the Sassanid Persians at the Battle of Satala and capture of their capital Ctesiphon in 298. Only the northwestern three of the eight pillars and parts of the masonry cores of the arches above survive.
The Rotunda is a cylindrical structure built in 306 AD on the orders of the Galerius, who was thought to have intended it to be his mausoleum.
The Rotunda has a diameter of 24.5 m. Its walls are more than 6 m thick, which is why it has withstood Thessaloniki's earthquakes. The walls are interrupted by eight rectangular bays, with the west bay forming the entrance. A flat brick dome, 30 m high at the peak, crowns the cylindrical structure. In its original design, the dome of the Rotunda had an oculus, as does the Pantheon in Rome.
After Galerius's death in 311, he was buried at Gamzigrad near Zajecar, Serbia. The Rotunda stood empty for several decades until the Emperor Theodosius I ordered its conversion into a Christian church in the late fourth century. The church was embellished with very high quality mosaics. Only fragments have survived of the original decoration, for example, a band depicting saints with hands raised in prayer, in front of complex architectural fantasies.
The building was used as a church (Church of Asomaton or Archangelon) for over 1,200 years until the city fell to the Ottomans. In 1590 it was converted into a mosque, called the Mosque of Suleyman Hortaji Effendi, and a minaret was added to the structure. It was used as a mosque until 1912, when the Greeks captured the city during the Balkan War. Greek Orthodox officials reconsecrated the structure as a church, and they left the minaret. The structure was damaged during an earthquake in 1978 but was subsequently restored. As of 2004, the minaret was still being stabilized with scaffolding. The building is now a historical monument under the Ephorate of Byzantine Antiquities of the Greek Ministry of Culture, although the Greek Orthodox Church has access to the monument for various festivities some days of the year.
The Rotunda is the oldest of Thessaloniki's churches. Some Greek publications claim it is the oldest Christian church in the world, although there are competitors for that title. It is the most important surviving example of a church from the early Christian period of the Greek-speaking part of the Roman Empire.References:
The Basilica of Santa Maria in Trastevere is one of the oldest churches of Rome. The basic floor plan and wall structure of the church date back to the 340s, and much of the structure to 1140-43. The first sanctuary was built in 221 and 227 by Pope Callixtus I and later completed by Pope Julius I.
The inscription on the episcopal throne states that this is the first church in Rome dedicated to Mary, mother of Jesus, although some claim that privilege belongs to the Basilica di Santa Maria Maggiore. A Christian house-church was founded here about 220 by Pope Saint Callixtus I (217-222) on the site of the Taberna meritoria, a refuge for retired soldiers. The area was made available for Christian use by Emperor Alexander Severus when he settled a dispute between the Christians and tavern-keepers.
The church underwent two restorations in the fifth and eighth centuries and in 1140-43 it was re-erected on its old foundations under Pope Innocent II.